Proceedings of the Third International Conference on Invasive ...

<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive SpartinaChapter 2: Spartina Distribution and SpreadBroad cover-class boundaries also contribute toimprecision. For example, if a polygon area is within a coverclass, e.g. 10-30%, <strong>the</strong>n it is assigned <strong>the</strong> midpoint <strong>of</strong> <strong>the</strong>class, 15% in this example. In both 2001 and 2003 CogswellMarsh fell within cover class 10-30%. Ei<strong>the</strong>r <strong>the</strong>re was nochange in cover between 2001 and 2003 or <strong>the</strong> differencewas not large enough for 2003 to be assigned to <strong>the</strong> nextlarger class. Thus, a trend <strong>of</strong> expansion or contraction willbe detected only when it crosses a cover class boundary.However, <strong>the</strong> cover classes are useful for determining anapproximate infestation level and can be used to prioritizeremoval efforts.Accuracy <strong>of</strong> Field IdentificationGenetic tests were also performed to confirm speciesidentification by field staff at each <strong>of</strong> <strong>the</strong> InventoryMonitoring Sites. The genetic tests confirmed that field staffwere accurately identifying both S. alterniflora hybrids(89%) and S. foliosa (100%). The samples labeled as“unknown” or “unidentifiable” by field staff were found justas likely to be hybrids as S. foliosa (55%-45%).Trained field biologists can accurately identify <strong>the</strong>majority <strong>of</strong> non-native Spartina plants, but genetic testing <strong>of</strong>ambiguous hybrid specimens is necessary to reduce <strong>the</strong> risk<strong>of</strong> overlooking non-natives and <strong>the</strong>ir hybrids.EfficacyPost-treatment monitoring was done at five sites thatwere treated in 2002 and pre-treatment monitoring wasdone at seven sites. Manual removal (digging) <strong>of</strong> S.densiflora at Piper Park was effective; however, a number<strong>of</strong> divots remained visible in <strong>the</strong> marsh plain severalmonths after <strong>the</strong> clones were removed. It is uncertain howlong <strong>the</strong>se features will remain in <strong>the</strong> marsh and it isunclear what effect <strong>the</strong>y may have on <strong>the</strong> quality <strong>of</strong> <strong>the</strong>marsh habitat. We observed that volunteer removal effortsare excellent for public outreach, but it was frequentlynecessary for organizers and ISP staff to complete workbegun by volunteers.Clones in Bolinas Lagoon and Point Reyes that hadbeen dug or trampled and covered were reduced by 95%.However, <strong>the</strong> clone that was dug out in Bolinas Lagooncontinued to produce some shoots around <strong>the</strong> clone edgethat required pulling. A single clone at Pier 98, which hadbeen partially dug out and covered with geo-textile fabricby volunteers, had a number <strong>of</strong> remaining shoots thatrequired fur<strong>the</strong>r control. Clones must be entirely coveredfor <strong>the</strong> treatment to be effective. Roots and rhizomesshould be confirmed dead as was done at Point Reyesbefore uncovering treated clones. Preliminary posttreatmentmonitoring <strong>of</strong> <strong>the</strong> Emeryville treatment site thatwas mowed in 2002 indicated no noticeable treatmenteffect.CONCLUSIONS AND RECOMMENDATIONSData from 28 sites showed that non-native Spartinaspecies are spreading at a rapid rate in <strong>the</strong> San Francisco BayEstuary. Between 2000-2001 and 2003, <strong>the</strong> average percentincrease in area covered by all non-native Spartina speciesin <strong>the</strong> Estuary was 244%, and by hybrids, 317%. Some siteshad several hundred percent increases. While hybridsincreased in area at all site types, spread was greatest forfringing tidal marshes, mudflats, and estuarine beaches (SiteType II). There was a slight trend in increase <strong>of</strong> hybrid coverwith latitude (south to north trend). Aerial photo areameasurements were compared with field measurements atfive sites where both methods were used in 2003. There wasno difference in <strong>the</strong> mean coverage between methods, butgiven <strong>the</strong> small sample size and that no regressionrelationship was found, aerial photo interpretationmeasurements should be used with caution to estimate fieldmeasurements for a single site. The increasingly rapid rate <strong>of</strong>spread <strong>of</strong> Spartina, in particular hybrids, continues tothreaten existing habitat and species assemblages andpotentially threatens <strong>the</strong> success <strong>of</strong> ongoing and plannedrestoration projects within <strong>the</strong> San Francisco Estuary andouter coast marshes. Successful control will only beachieved with dedication <strong>of</strong> adequate resources, attention t<strong>of</strong>ollowing protocols completely, and follow-up monitoringand periodic re-treatment as needed.ACKNOWLEDGMENTSFunding for <strong>the</strong> Monitoring Program was provided by<strong>the</strong> California Coastal Conservancy and <strong>the</strong> CalFed BayDelta Program (Interagency agreement 4600001875).Thank you to Alex Lee who performed <strong>the</strong> geneticanalyses and to Aimee Good, Johanna Good, TrippMcCandlish, Erik Grijalva, numerous landowners,managers, and stakeholders for <strong>the</strong>ir able assistance with <strong>the</strong>fieldwork. We also thank Peggy Ol<strong>of</strong>son, Director <strong>of</strong> <strong>the</strong>Invasive Spartina Project, and Patricia Bossak and MaxeneSpellman <strong>of</strong> <strong>the</strong> California Coastal Conservancy for <strong>the</strong>iradministrative and staff assistance. Peggy Ol<strong>of</strong>son andOliver Burke deserve special thanks for <strong>the</strong>ir editorialassistance.REFERENCESAnttila, C.K, A.R. King, C. Ferris, D.R. Ayres, and D.R. Strong.2000. Reciprocal hybrid formation <strong>of</strong> Spartina in San FranciscoBay. Molecular Ecology 9:765-771.Anttila, C.K., C.C. Daehler, N.E. Rank, and D.R Strong. 1998.Greater male fitness <strong>of</strong> a rare invader (Spartina alterniflora,Poaceae) threatens a common native (S. foliosa) with hybridization.American Journal <strong>of</strong> Botany 85:1597-1601.ArcView 3.3 (2002). Environmental Systems Research Institute,Inc. (ESRI), 380 New York Street, Redlands, California.http://www.esri.com.Ayres, D.R., K. Zaremba, C.M. Sloop, D.R.Strong. 2008. Sexualreproduction <strong>of</strong> cordgrass hybrids (Spartina foliosa x al--81-